Instead of sleeping in one long nap, chinstrap penguins break it up into several short naps of just a few seconds to constantly keep watch over their eggs and chicks.
A chinstrap penguin on King George Island, Antarctica. Photo: Paul-Antoine Libourel/Science
Chinstrap penguins ( Pygoscelis antarcticus ) on King George Island, Antarctica, take more than 10,000 naps a day. These four-second naps help the penguins keep watch over their nests, protecting their eggs and chicks from predators. In total, they sleep about 11 hours a day. The new study, conducted by Paul-Antoine Libourel at the Lyon Neuroscience Research Center and colleagues, was published in the journal Science on November 30.
On King George Island, the brown skua ( Stercorarius antarcticus ) is one of the main predators of chinstrap penguin eggs. Brown skuas often take unguarded eggs, mainly from fringe nests.
Pairs of chinstrap penguins often split up to forage for food, with one going out to sea while the other stays behind to guard the nest. As a result, the home bird must constantly guard its eggs or chicks, preventing them from being attacked by predators such as skuas or other penguins.
In the new study, the team monitored 14 penguins with eggs in their nests. They used data loggers to measure sleep-related brain activity and changes in body posture. The researchers found that the nest-keeping penguins could sleep both lying down and standing up, and that nearly 72 percent of their short-wave sleep (SWS) occurred in bursts of less than 10 seconds.
Parent penguins have about 600 SWS episodes per hour. However, when incubating their eggs in the nest, they experience more SWS, broken up into shorter bursts. Sleep depth increases slightly around midday, when the risk of predation may be lowest.
Another interesting finding was that penguins nesting at the outer edges of the colony actually slept better and had longer SWS periods than those nesting closer to the center, contrary to what the team had previously expected. This suggests that the need to be vigilant against predators like skua may not be so great. Instead, nest-raiding penguins may be a more immediate threat.
Thu Thao (According to IFL Science )
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